A burner for a gas turbine is known from U.S. Pat. No. 6,202,401. This burner is designed as a hybrid burner and operates as either diffusion or a pre-mix burner. Whereas with diffusion combustion, fuel and combustion air are mixed in the flame, with pre-mix combustion the combustion air is initially intensively mixed with the fuel and this mixture is then fed in for combustion. This is especially advantageous as regards nitrogen oxide emissions, since there is an even temperature in the precombustion flame because of the homogeneous mixture. Generation of nitrogen oxide increases exponentially with the flame temperature.
With pre-mix combustion a leaner combustion can take place so that there is a higher ratio of combustion air to fuel present than with diffusion combustion. This in its turn reduces generation of nitrogen oxide. However a leaner combustion has a greater tendency to produce combustion instabilities and has a smaller range of regulation than diffusion combustion. Therefore pre-mix combustion is frequently stabilized by a diffusion flame. However, the fact that with this system nitrogen oxide is generated in the diffusion means that the benefit of nitrogen oxide reduction from leaner pre-mix combustion is to some extent exhausted again.
With a burner system known from U.S. Pat. No. 3,954,384 a fuel feed system supplies a main burner and a pilot burner that lights the main burner. The flame of the pilot burner is monitored by a vessel containing porous material that is used for absorption of a gas to be analyzed.
EP 1062461 A1 shows a combustion chamber with a cladding of heat shield elements. A heat shield element is designed as a burner heat shield element to which combustion air and fuel are fed. In a possible embodiment the heat shield element is designed as a porous burner. The combustion reaction here takes place at least partly in a porous material. This stabilizes the combustion and reduces the tendency for formation of combustion variations.
In EP 0576697 B1 a gas turbine is described in which catalytic burners are also used in addition to classical burner types. The classical burner types are pre-mix burners with which main combustion is undertaken. Combination with catalytic burners allows easier regulation for changing load states of the gas turbine.